Polypropylene cable material with high water tree resistance as well as preparation method and application of polypropylene cable material

Abstract

The invention belongs to the technical field of cable materials, and particularly relates to a polypropylene cable material with high water tree resistance as well as a preparation method and application. According to the polypropylene cable material with the high water tree resistance, the maleic anhydride and other polar compounds are used for grafting and modifying polypropylene in advance, so that the polarity of the polypropylene and the polarity of the modified elastomer are similar, defects in the polypropylene cable material are reduced, and the water tree resistance of the polypropylene cable material is improved; good mechanical performance, electrical performance and thermal performance are maintained; in addition, by improving the dosage of the raw materials, the water tree resistance of the polypropylene cable material is further improved; therefore, the technical problem that a polypropylene cable material in the prior art lacks water tree resistance is solved.

Description

Technical Field

[0001] This application belongs to the technical field of cable materials, and particularly relates to a polypropylene cable material with high water tree resistance, a preparation method thereof, and an application thereof. Background Art

[0002] Crosslinked polyethylene has good insulation performance, is easy to manufacture, and has simple laying and installation. It is the main insulation material for current power cables. However, due to its crosslinked network molecular structure, it cannot be remelted and processed again, cannot be recycled, and is not conducive to promoting the green transformation of energy and power.

[0003] In recent years, with the increasing improvement of plastic synthesis and molding technologies, thermoplastic polypropylene cable materials with higher service temperatures and no need for crosslinking have gradually been applied in medium and high-voltage power cables. Usually, polypropylene has a high hardness and cannot be directly used as a cable insulation material. It needs to be modified. The usual modification method is to melt-blend polypropylene with an elastomer material using a mixing equipment, which can effectively reduce the hardness of the material and improve its toughness, making it meet the mechanical requirements of polypropylene cable materials.

[0004] However, there is a problem of water tree aging in polypropylene cable insulation materials. Water tree aging occurs in power cable insulation materials during long-term operation. Due to the intrusion of moisture and the action of an electric field, dendritic structures will form in the insulation material. Water tree aging usually does not cause immediate insulation failure, but water trees can initiate and grow at a lower electric field strength, seriously affecting the electrical performance of the insulation, and even inducing insulation electrical breakdown. Water tree aging is one of the main problems affecting the operation reliability and service life of power cables. By using waterproof structures such as metal wires, aluminum-plastic composite tapes, and metal sheaths, the water tree aging phenomenon can be reduced, and the operation reliability and service life of power cables can be improved. However, the use of cable waterproof structures increases the complexity and preparation cost of cable preparation, which is not conducive to the large-scale application of polypropylene power cables. By improving the polypropylene cable material itself and enhancing its water tree resistance, it is expected to fundamentally reduce the occurrence of water tree aging problems in polypropylene cable materials. Summary of the Invention

[0005] In view of this, this application provides a polypropylene cable material with high water tree resistance, a preparation method thereof, and an application thereof, which are used to solve the technical problem that polypropylene cable materials in the prior art lack water tree resistance.

[0006] In the first aspect of this application, a polypropylene cable material with high water tree resistance is provided, and the raw materials include: compatibilized polypropylene, modified elastomer, and antioxidant.

[0007] The modified elastomer is prepared by melt-blending an elastomer base material, a polar graft-modified elastomer, a polar water tree inhibitor, and an antioxidant.

[0008] The compatibilized polypropylene is prepared by melt blending a polypropylene base material, a polar graft-modified polypropylene, and an antioxidant.

[0009] Preferably, the polar groups introduced into the molecular chain of the polar graft-modified elastomer and the polar groups introduced into the molecular chain of the polar graft-modified polypropylene are the same polar groups.

[0010] Preferably, the polar graft-modified elastomer is selected from elastomers graft-modified with maleic anhydride, glycidyl methacrylate, or acrylate compounds;

[0011] The polar graft-modified polypropylene is selected from polypropylenes graft-modified with maleic anhydride, glycidyl methacrylate, or acrylate compounds.

[0012] Preferably, calculated by mass parts, the polypropylene cable material with high water tree resistance includes: 40-100 mass parts of compatibilized polypropylene, 20-80 mass parts of modified elastomer, and 0.1-1.0 mass parts of antioxidant.

[0013] Preferably, the polypropylene cable material with high water tree resistance includes: 50-70 mass parts of compatibilized polypropylene, 30-50 mass parts of modified elastomer, and 0.2-0.5 mass parts of antioxidant.

[0014] The second aspect of the present application provides a preparation method of a polypropylene cable material with high water tree resistance, which can prepare a polypropylene cable material with high water tree resistance as described in the first aspect. The preparation method includes the following steps:

[0015] The step of preparing the modified elastomer: melt blend an elastomer base material, a polar graft-modified elastomer, a polar water tree inhibitor, and an antioxidant to obtain a modified elastomer;

[0016] The step of preparing the compatibilized polypropylene: melt blend a polypropylene base material, a polar graft-modified polypropylene, and an antioxidant to obtain a compatibilized polypropylene;

[0017] The step of preparing the polypropylene cable material: melt blend the compatibilized polypropylene, the modified elastomer, and the antioxidant to obtain a polypropylene cable material with high water tree resistance.

[0018] Preferably, in the step of preparing the modified elastomer, the polar water tree inhibitor used is selected from at least one of ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer, and polyethylene glycol.

[0019] Preferably, in the step of preparing the modified elastomer, the mass ratio of the elastomer base material, the polar graft-modified elastomer, the polar water tree inhibitor, and the antioxidant is: 50-150:1-5:2-10:0.1-1.0;

[0020] In the steps of preparing the compatibilized polypropylene, the mass ratio of the polypropylene base material, the polar graft-modified polypropylene, and the antioxidant used is: 50~150: 1~4: 0.1~1.0;

[0021] In the steps of preparing the polypropylene cable material, the mass ratio of the compatibilized polypropylene, the modified elastomer, and the antioxidant used is: 40~100: 20~80: 0.1~1.0.

[0022] Preferably, in the steps of preparing the compatibilized polypropylene, the mass ratio of the polypropylene base material, the polar graft-modified polypropylene, and the antioxidant used is: 90~110: 1~4: 0.1~0.3.

[0023] Preferably, in the steps of preparing the modified elastomer, the mass ratio of the elastomer base material, the polar graft-modified elastomer, the polar water tree inhibitor, and the antioxidant used is: 90~110: 2~3: 5~9: 0.1~0.3.

[0024] Preferably, in the steps of preparing the modified elastomer, the elastomer base material used is selected from at least one of styrene-ethylene-butene-styrene block copolymer, ethylene-octene copolymer, polystyrene-polyolefin-polystyrene block copolymer, and ethylene propylene diene monomer rubber.

[0025] Preferably, in the steps of preparing the compatibilized polypropylene, the polypropylene base material used is selected from homopolypropylene and / or copolymerized polypropylene.

[0026] Preferably, in the steps of preparing the modified elastomer, the steps of preparing the compatibilized polypropylene, and the steps of preparing the polypropylene cable material, the antioxidant used is selected from at least one of antioxidant 1010, antioxidant 1035, and antioxidant 300.

[0027] Preferably, in the steps of preparing the modified elastomer, the steps of preparing the compatibilized polypropylene, and the steps of preparing the polypropylene cable material, the temperature of melt blending is 170~190°C, the rotation speed is 25~75 r / min, and the time is 3~10 min.

[0028] Preferably, after the steps of preparing the polypropylene cable material, it further includes a hot pressing and forming step, and the polypropylene cable material with high water tree resistance performance is heated and melted, pressure-increased and melted, and cooled and formed in sequence to obtain the polypropylene cable material after hot pressing and forming.

[0029] The third aspect of the present application provides an application of the polypropylene cable material with high water tree resistance performance described in the first aspect in the preparation of power cables.

[0030] The fourth aspect of the present application provides a polypropylene power cable with high water tree resistance performance, and the insulating layer in the polypropylene power cable is selected from a polypropylene cable material with high water tree resistance performance described in the first aspect.

[0031] Compared with the prior art, a polypropylene power cable with high water tree resistance performance provided by the present application has at least the following beneficial effects:

[0032] 1. For a polypropylene cable material with high water tree resistance performance provided by the present application, by pre-grafting and modifying polypropylene with polar compounds such as maleic anhydride, the polarity of polypropylene and the modified elastomer is made similar, reducing the formation of defects in the polypropylene cable material, thereby inhibiting the development channels of water trees in the polypropylene cable material and improving the water tree resistance performance of the polypropylene cable material; at the same time, it also meets the engineering requirements in terms of mechanical properties, electrical properties and thermal properties.

[0033] 2. For a polypropylene cable material with high water tree resistance performance provided by the present application, during the preparation process of the polypropylene cable material, by improving the raw material dosage of the prepared modified elastomer and polypropylene, the water tree resistance performance of the polypropylene cable material is further improved.

[0034] 3. For a polypropylene cable material with high water tree resistance performance provided by the present application, the SEBS, SEBS-g-MAH, EAA, PP, PP-g-MAH and antioxidants used are all raw materials for large-scale industrial production, which can reduce the supply chain pressure during the production of the polypropylene cable material and is conducive to the large-scale popularization and application of the polypropylene cable material with high water tree resistance performance provided by the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0036] Figure 1 It is a water tree morphology diagram obtained by performing water tree aging characteristic tests on the polypropylene cable materials and water tree-resistant cross-linked polyethylene cable materials provided in Examples 1-4 and Comparative Example 1 of the present application;

[0037] Figure 2 It is a statistical chart of water tree lengths obtained by performing water tree aging characteristic tests on the polypropylene cable materials and water tree-resistant cross-linked polyethylene cable materials provided in Examples 1-4 and Comparative Example 1 of the present application;

[0038] Figure 3Graph showing the mechanical property test results of the polypropylene cable materials provided in Examples 1-4 and Comparative Example 1 of this application;

[0039] Figure 4 Melting curve graph in the thermal property test of the polypropylene cable materials provided in Examples 1-4 and Comparative Example 1 of this application;

[0040] Figure 5 Crystallization curve graph in the thermal property test of the polypropylene cable materials provided in Examples 1-4 and Comparative Example 1 of this application;

[0041] Figure 6 Graph showing the electrical property test results of the polypropylene cable materials, water-tree resistant crosslinked polyethylene cable materials provided in Examples 1-4 and Comparative Example 1 of this application. Detailed implementation manners

[0042] This application provides a polypropylene cable material with high water-tree resistance, a preparation method and an application, aiming to solve the technical problem that the polypropylene cable material in the prior art lacks water-tree resistance.

[0043] The technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are part of the embodiments of this application, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts shall fall within the scope of protection of this application.

[0044] In view of the current low water tree resistance performance of polypropylene cable materials, it is necessary to improve the polypropylene cable materials themselves to enhance their water tree resistance performance and reduce the water tree aging problem of polypropylene cable materials at the source. This application provides a polypropylene cable material with high water tree resistance performance, and the raw materials used include compatibilized polypropylene, modified elastomer, and antioxidant. Among them, the modified elastomer is prepared by melt blending an elastomer base material, a polar graft-modified elastomer, a polar water tree inhibitor, and an antioxidant. The introduction of the elastomer base material can effectively reduce the hardness of the polypropylene material and improve its toughness. The introduction of the polar water tree inhibitor can enhance the water tree resistance performance of the polypropylene cable material. The introduction of the polar graft-modified elastomer can promote the effective dispersion of the polar water tree inhibitor in the elastomer base material during melt blending, and the effect of the polar water tree inhibitor can be fully exerted. However, this will increase the polarity of the modified elastomer, resulting in a greater difference from non-polar polypropylene, and the compatibility between compatibilized polypropylene and the modified elastomer will also decrease. The prepared polypropylene cable material is prone to forming defects, and the defects serve as the development channels for water trees, resulting in a decline in the water tree resistance performance of the polypropylene cable material. And in this application, by using compatibilized polypropylene prepared by melt blending a polypropylene base material, a polar graft-modified polypropylene, and an antioxidant in the polypropylene cable material, since the polar graft-modified polypropylene is introduced into the polypropylene base material, the polarity of the non-polar polypropylene base material is increased, making the compatibility between polypropylene and the modified elastomer good and not easily forming defects, thereby enhancing the water tree resistance performance of the current polypropylene cable material. Therefore, this application provides a polypropylene cable material with high water tree resistance performance.

[0045] Preferably, in the polypropylene cable material with high water tree resistance performance provided by this application, the polar groups introduced into the molecular chains of the polar graft-modified elastomer and the polar graft-modified polypropylene are the same, further reducing the formation of defects in the polypropylene cable material and improving the water tree resistance performance of the polypropylene cable material. And for the polar graft-modified elastomer in the polypropylene cable material, it can be selected from maleic anhydride, glycidyl methacrylate, or acrylate compound graft-modified elastomer, and the polar graft-modified polypropylene can be selected from maleic anhydride, glycidyl methacrylate, or acrylate compound graft-modified polypropylene.

[0046] Correspondingly, the present application also provides a method for preparing the polypropylene cable material with high water tree resistance performance, including the steps of melt blending an elastomer base material, a polar graft-modified elastomer, a polar water tree inhibitor and an antioxidant to prepare a modified elastomer, melt blending a polypropylene base material, a polar graft-modified polypropylene and an antioxidant to prepare a compatibilized polypropylene, and melt blending the compatibilized polypropylene, the modified elastomer and an antioxidant to prepare a polypropylene cable material; correspondingly, the present application also provides the common hot pressing forming steps for polypropylene materials, heating and melting the polypropylene cable material in sequence, boosting the pressure for melting, and cooling and forming to obtain the polypropylene cable material after hot pressing forming, and the polypropylene cable material after hot pressing forming can be in the shape of a cable insulating layer.

[0047] Preferably, in the process of preparing the modified elastomer in the method for preparing the polypropylene cable material with high water tree resistance performance of the present application, polar water tree inhibitors such as ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer, polyethylene glycol, etc. are introduced; on the one hand, polar water tree inhibitors such as polyethylene glycol are high-yield chemical products, and the raw materials are easy to obtain. On the other hand, these chemical products are novel polar water tree inhibitors. The ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer, and polyethylene glycol contain polar groups such as carboxyl (-COOH) and hydroxyl (-OH), which can form hydrogen bonds with water molecules, fix the water, reduce its free diffusion, reduce the occurrence of insulation water tree aging phenomena caused by water intrusion and electric field action, and improve the water tree aging resistance performance of the polypropylene cable material.

[0048] Preferably, in the method for preparing the polypropylene cable material with high water tree resistance performance of the present application, the dosages of raw materials are also controlled. When the mass ratio of the polypropylene base material, the polar graft-modified polypropylene, and the antioxidant used in the step of preparing the compatibilized polypropylene is 90-110:1-4:0.1-0.3, and the mass ratio of the elastomer base material, the polar graft-modified elastomer, the polar water tree inhibitor and the antioxidant used in the step of preparing the modified elastomer is 90-110:2-3:5-9:0.1-0.3, the water tree resistance performance of the polypropylene cable material will be improved, the initiation rate of water trees will be reduced, and the length of water trees will be decreased.

[0049] As an application, the present application provides the application of the above polypropylene cable material with high water tree resistance performance in the preparation of power cables, such as directly making an insulating layer or adding conductive materials such as carbon black to make a shielding layer, etc.

[0050] Correspondingly, the present application also provides a polypropylene cable with high water tree resistance performance, and the insulating layer in this polypropylene cable uses the polypropylene cable material with high water tree resistance performance provided by the present application.

[0051] The following will specifically describe the polypropylene cable material with high water tree resistance performance provided by this application in combination with examples and experimental examples.

[0052] Example 1

[0053] The preparation method of the polypropylene cable material with high water tree resistance performance provided in Example 1 of this application includes the steps of preparing a modified elastomer, preparing a compatibilized polypropylene, preparing a polypropylene cable material, and hot pressing and forming.

[0054] The step of preparing a modified elastomer: Add styrene-ethylene-butene-styrene block copolymer SEBS, maleic anhydride grafted styrene-ethylene-butene-styrene block copolymer SEBS-g-MAH, ethylene-acrylic acid copolymer EAA, and antioxidant 300 into a torque rheometer according to a mass ratio of 1000g:25g:50g:2g, control the temperature at 180°C and the rotation speed at 50 r / min, carry out melt blending for 7 min, and then cool and pelletize to obtain a modified elastomer;

[0055] The step of preparing a compatibilized polypropylene: Add polypropylene PP, maleic anhydride grafted polypropylene PP-g-MAH, and antioxidant 300 into a torque rheometer according to a mass ratio of 1000g:16.7g:2g, control the temperature at 180°C and the rotation speed at 50 r / min, carry out melt blending for 5 min, and then cold pelletize to obtain a compatibilized polypropylene;

[0056] The step of preparing a polypropylene cable material: Add the compatibilized polypropylene, modified elastomer, and antioxidant 1010 into a torque rheometer according to a mass ratio of 600g:400g:3g, control the temperature at 180°C and the rotation speed at 50 r / min, carry out melt blending for 5 min, and then cold pelletize to obtain a polypropylene cable material with high water tree resistance performance, which is a polypropylene cable material with high water tree resistance performance;

[0057] The step of hot pressing and forming: Use a flat vulcanizing machine to melt the prepared polypropylene cable material at 180°C for 20 min without pressure first, and then use a method of gradually increasing the pressure to carry out pressure application in sequence from 0, 5, 10, 15 MPa, melt for 5 min at each pressure, and then place the sample in a water-cooled vulcanizing machine, directly increase the pressure to 15 MPa until it is cooled and taken out to obtain the polypropylene cable material after hot pressing and forming.

[0058] Example 2

[0059] The preparation method of the polypropylene cable material with high water tree resistance performance provided in Example 2 of this application is different from that of Example 1 in the raw material dosage of the modified elastomer, including the steps of preparing a modified elastomer, preparing a compatibilized polypropylene, preparing a polypropylene cable material, and hot pressing and forming.

[0060] Steps for preparing a modified elastomer: Add styrene-ethylene-butene-styrene block copolymer (SEBS), maleic anhydride grafted styrene-ethylene-butene-styrene block copolymer (SEBS-g-MAH), ethylene-acrylic acid copolymer (EAA), and antioxidant 300 into a torque rheometer according to a mass ratio of 1000 g: 25 g: 75 g: 2 g, control the temperature at 180 °C and the rotation speed at 50 r / min, conduct melt blending for 7 min, and then cool and pelletize to obtain the modified elastomer;

[0061] Steps for preparing a compatibilized polypropylene: Add polypropylene (PP), maleic anhydride grafted polypropylene (PP-g-MAH), and antioxidant 300 into a torque rheometer according to a mass ratio of 1000 g: 16.7 g: 2 g, control the temperature at 180 °C and the rotation speed at 50 r / min, conduct melt blending for 5 min, and then cool and pelletize to obtain the compatibilized polypropylene;

[0062] Steps for preparing a polypropylene cable material: Add the compatibilized polypropylene, the modified elastomer, and antioxidant 1010 into a torque rheometer according to a mass ratio of 600 g: 400 g: 3 g, control the temperature at 180 °C and the rotation speed at 50 r / min, conduct melt blending for 5 min, and then cool and pelletize to obtain the polypropylene cable material, which has high water tree resistance and is a polypropylene cable material with high water tree resistance;

[0063] Steps for hot pressing and molding: Use a flat vulcanizing machine to melt the prepared polypropylene cable material at 180 °C without pressure for 20 min first, and then, by the method of gradually increasing the pressure, conduct pressure application in sequence from 0, 5, 10, and 15 MPa, melt for 5 min under each pressure, then place the sample into a water-cooled vulcanizing machine, directly increase the pressure to 15 MPa, and keep it until it is cooled and taken out to obtain the polypropylene cable material after hot pressing and molding.

[0064] Example 3

[0065] The present application provides a preparation method of a polypropylene cable material with high water tree resistance in Example 3. The difference between the preparation method and that in Example 1 lies in the raw material dosages of the modified elastomer and the compatibilized polypropylene. The preparation method includes steps for preparing the modified elastomer, steps for preparing the compatibilized polypropylene, steps for preparing the polypropylene cable material, and steps for hot pressing and molding.

[0066] Steps for preparing a modified elastomer: Add styrene-ethylene-butene-styrene block copolymer SEBS, maleic anhydride grafted styrene-ethylene-butene-styrene block copolymer SEBS-g-MAH, ethylene-acrylic acid copolymer EAA, and antioxidant 300 into a torque rheometer according to a mass ratio of 1000 g: 25 g: 50 g: 2 g, control the temperature at 180 °C and the rotation speed at 50 r / min, carry out melt blending for 7 min, and then cool and pelletize to obtain the modified elastomer;

[0067] Steps for preparing a compatibilized polypropylene: Add polypropylene PP, maleic anhydride grafted polypropylene PP-g-MAH, and antioxidant 300 into a torque rheometer according to a mass ratio of 1000 g: 33.3 g: 2 g, control the temperature at 180 °C and the rotation speed at 50 r / min, carry out melt blending for 5 min, and then cool and pelletize to obtain the compatibilized polypropylene;

[0068] Steps for preparing a polypropylene cable material: Add the compatibilized polypropylene, the modified elastomer, and antioxidant 1010 into a torque rheometer according to a mass ratio of 600 g: 400 g: 3 g, control the temperature at 180 °C and the rotation speed at 50 r / min, carry out melt blending for 5 min, and then cool and pelletize to obtain the polypropylene cable material, which has high water tree resistance performance and is a polypropylene cable material with high water tree resistance performance;

[0069] Steps for hot pressing and forming: Use a flat vulcanizing machine to melt the prepared polypropylene cable material at 180 °C without pressure for 20 min first, and then, by means of gradually increasing the pressure, carry out pressurization successively from 0, 5, 10, and 15 MPa, melt for 5 min under each pressure, then place the sample in a water-cooled vulcanizing machine, and directly increase the pressure to 15 MPa until it is cooled and taken out to obtain the polypropylene cable material after hot pressing and forming.

[0070] Example 4

[0071] Example 4 of this application provides a preparation method of a polypropylene cable material with high water tree resistance performance. The difference between the preparation method and that of Example 1 lies in the raw material dosages of the modified elastomer and the compatibilized polypropylene, including the steps of preparing the modified elastomer, preparing the compatibilized polypropylene, preparing the polypropylene cable material, and hot pressing and forming.

[0072] Steps for preparing a modified elastomer: Add styrene-ethylene-butene-styrene block copolymer SEBS, maleic anhydride grafted styrene-ethylene-butene-styrene block copolymer SEBS-g-MAH, ethylene-acrylic acid copolymer EAA, and antioxidant 300 into a torque rheometer according to a mass ratio of 1000 g: 25 g: 75 g: 2 g, control the temperature at 180 °C and the rotation speed at 50 r / min, carry out melt blending for 7 min, and then cool and pelletize to obtain the modified elastomer;

[0073] Steps for preparing compatibilized polypropylene: Add polypropylene (PP), maleic anhydride grafted polypropylene (PP-g-MAH), and antioxidant 300 into a torque rheometer according to a mass ratio of 1000 g: 33.3 g: 2 g, control the temperature at 180 °C and the rotation speed at 50 r / min, conduct melt blending for 5 min, and then granulate by cold cutting to obtain compatibilized polypropylene;

[0074] Steps for preparing polypropylene cable material: Add compatibilized polypropylene, modified elastomer, and antioxidant 1010 into a torque rheometer according to a mass ratio of 600 g: 400 g: 3 g, control the temperature at 180 °C and the rotation speed at 50 r / min, conduct melt blending for 5 min, and then granulate by cold cutting to obtain polypropylene cable material, which has high water tree resistance and is a polypropylene cable material with high water tree resistance;

[0075] Steps for hot pressing and forming: Use a flat vulcanizing machine to melt the prepared polypropylene cable material at 180 °C for 20 min without applying pressure first, and then gradually increase the pressure from 0, 5, 10, and 15 MPa in sequence, conduct melting for 5 min at each pressure, then place the specimen in a water-cooled vulcanizing machine, directly increase the pressure to 15 MPa, and keep it until it is cooled and taken out to obtain the polypropylene cable material after hot pressing and forming.

[0076] Comparative Example 1

[0077] Comparative Example 1 of the present application provides a preparation method of polypropylene cable material, and the preparation method includes steps for preparing modified elastomer, steps for preparing polypropylene cable material, and steps for hot pressing and forming.

[0078] Steps for preparing modified elastomer: Add styrene-ethylene-butene-styrene block copolymer (SEBS), maleic anhydride grafted styrene-ethylene-butene-styrene block copolymer (SEBS-g-MAH), ethylene-acrylic acid copolymer (EAA), and antioxidant 300 into a torque rheometer according to a mass ratio of 1000 g: 25 g: 50 g: 2 g, control the temperature at 180 °C and the rotation speed at 50 r / min, conduct melt blending for 7 min, and then cool and granulate to obtain modified elastomer;

[0079] Steps for preparing polypropylene cable material: Add polypropylene, modified elastomer, and antioxidant 1010 into a torque rheometer according to a mass ratio of 600 g: 400 g: 3 g, control the temperature at 180 °C and the rotation speed at 50 r / min, conduct melt blending for 5 min, and then granulate by cold cutting to obtain polypropylene cable material;

[0080] Steps of hot pressing molding: The prepared polypropylene cable material is melted without pressure for 20 minutes at a temperature of 180 °C using a flat vulcanizing machine, and then pressurized step by step from 0, 5, 10, and 15 MPa in sequence, with melting for 5 minutes under each pressure. Then, the specimen is placed in a water-cooled vulcanizing machine, directly pressurized to 15 MPa, and taken out until cooled to obtain the polypropylene cable material after hot pressing molding.

[0081] Experimental Example 1

[0082] In Experimental Example 1 of this application, performance tests were carried out on the polypropylene cable materials provided in Examples 1-4 and Comparative Example 1, as well as a commercially available medium-voltage water-tree resistant cross-linked polyethylene cable material. The performance tests included water-tree aging characteristic tests, mechanical property tests, thermal property tests, and electrical property tests.

[0083] The water-tree aging characteristic test was carried out using the water knife electrode method. The steps included: First, the polypropylene cable materials provided in Examples 1-4 and Comparative Example 1, and the water-tree resistant cross-linked polyethylene cable material were respectively made into samples with a length and width of 100 mm and a thickness of 4 mm. Among them, the sample made of the water-tree resistant cross-linked polyethylene cable material was recorded as the sample of Comparative Example 2. Subsequently, during the water-tree aging characteristic test, the effective value of the power supply voltage during the test was 4 kV, the frequency was 3.5 kHz, the knife-edge defect was formed with a knife tip having a length of 40 mm, a width of 0.03 mm, and a tip curvature radius of 0.01 mm, and the distance from the tip of the knife-edge defect to the other surface of the specimen was 2 mm. The concentration of the NaCl solution was 1.8 mol / L, and the aging time was 7 days. After the water-tree aging characteristic test, the knife-edge defect of the specimen was vertically cut into slices with a thickness of about 120 μm along its length direction and stained with methylene blue solution, and the water-tree morphology and size were observed with a microscope, and the water-tree initiation rate was calculated. The results are as Figure 1-2 shown in Table 1; From Figure 1-2 and Table 1, it can be seen that the water-tree resistance of the polypropylene cable material provided in Comparative Example 1 is slightly lower than that of the water-tree resistant cross-linked polyethylene cable material provided in Comparative Example 2. However, the polypropylene cable materials provided in Examples 1-4 have very excellent water-tree resistance. After the polypropylene material is pre-modified with a polar compound such as maleic anhydride and then added to the modified elastomer material to make the insulating material, the water-tree resistance of the insulating material can be slightly increased by about 25-75% (the average length of the water tree is reduced by about 25-75%), and at the same time, it also has a lower water-tree initiation rate.

[0084] The steps of the mechanical property test include: referring to the regulations in the standard of GB / T 1040.3-2006 for tensile experiments, making dumbbell-shaped specimens from the polypropylene cable materials provided in Examples 1-4 and Comparative Example 1, and then carrying out mechanical property tests. The results are as Figure 3 shown; From Figure 3It can be seen that the breaking stress of the polypropylene cable materials provided in Embodiments 1-4 of the present application can be higher than 20 MPa, while the elongation at break is around 600%. Their performance is comparable to that of the polypropylene cable material provided in Comparative Example 1, and they can meet the engineering requirements in terms of mechanical properties.

[0085] The steps of the thermal performance test include: testing the melting curve and crystallization curve of the polypropylene cable materials provided in Embodiments 1-4 and Comparative Example 1 by a DSC differential scanning calorimeter, and the results are as Figure 4-5 shown; from Figure 4-5 it can be seen that there are no obvious changes in the melting curves and crystallization curves of several polypropylene cable materials. The addition of maleic anhydride grafted polypropylene in Embodiments 1-4 does not affect their crystallization characteristics. The melting temperature and crystallization temperature of the polypropylene cable materials provided in Embodiments 1-4 and Comparative Example 1 are almost the same, indicating that the modification method in the present application will not affect the temperature resistance ability of the polypropylene cable materials.

[0086] The steps of the electrical performance test include: referring to the regulations in the standard of GB / T 1408.1-2016, testing the breakdown field strength of the polypropylene cable materials provided in Embodiments 1-4 and Comparative Example 1 and the water-tree resistant cross-linked polyethylene cable materials at power frequency (50 Hz). Among them, the samples made of the water-tree resistant cross-linked polyethylene cable materials are recorded as the samples of Comparative Example 2, and the characteristic value of the breakdown field strength of the materials is obtained through the Weibull distribution to characterize the electrical strength resistance of the materials; the results are as Figure 6 shown, from Figure 6 it can be seen that the electrical strength resistance at power frequency of the polypropylene cable materials provided in Embodiments 1-4 of the present application is similar to that of the polypropylene cable material provided in Comparative Example 1, and they can meet the engineering requirements in terms of electrical performance.

[0087] Table 1: Water tree initiation rate

[0088]

[0089] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A polypropylene cable material with high resistance to water treeing, characterized in that, Comprising: Compatibilized polypropylene, modified elastomer and antioxidant; The modified elastomer is prepared by melt blending an elastomer base material, a polar graft-modified elastomer, a polar water tree inhibitor and an antioxidant; The compatibilized polypropylene is prepared by melt blending a polypropylene base material, a polar graft-modified polypropylene and an antioxidant.

2. The polypropylene cable material with high water tree resistance according to claim 1, characterized in that The polar groups introduced into the molecular chain of the polar graft-modified elastomer and the polar groups introduced into the molecular chain of the polar graft-modified polypropylene are the same polar groups.

3. The polypropylene cable material with high water tree resistance according to claim 1, characterized in that, The polar graft-modified elastomer is selected from elastomers graft-modified with maleic anhydride, glycidyl methacrylate or acrylate compounds; The polar graft-modified polypropylene is selected from polypropylenes graft-modified with maleic anhydride, glycidyl methacrylate or acrylate compounds.

4. A preparation method of a polypropylene cable material with high water tree resistance performance, characterized in that, For preparing a polypropylene cable material with high water tree resistance according to any one of claims 1-3, comprising the following steps: The step of preparing the modified elastomer, melt blending the elastomer base material, the polar graft-modified elastomer, the polar water tree inhibitor and the antioxidant to obtain the modified elastomer; The step of preparing the compatibilized polypropylene, melt blending the polypropylene base material, the polar graft-modified polypropylene and the antioxidant to obtain the compatibilized polypropylene; The step of preparing the polypropylene cable material, melt blending the compatibilized polypropylene, the modified elastomer and the antioxidant to obtain the polypropylene cable material with high water tree resistance.

5. The preparation method of a polypropylene cable material with high resistance to water tree according to claim 4, characterized in that, In the step of preparing the modified elastomer, the polar water tree inhibitor used is selected from at least one of ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer, polyethylene glycol.

6. The preparation method of a polypropylene cable material with high water tree resistance according to claim 4, characterized in that, In the step of preparing the modified elastomer, the mass ratio of the elastomer base material, the polar graft-modified elastomer, the polar water tree inhibitor and the antioxidant is: 50~150:1~5:2~10:0.1~1.0; In the step of preparing the compatibilized polypropylene, the mass ratio of the polypropylene base material, the polar graft-modified polypropylene and the antioxidant is: 50~150:1~4:0.1~1.0; In the step of preparing the polypropylene cable material, the mass ratio of the compatibilized polypropylene, the modified elastomer and the antioxidant is: 40~100:20~80:0.1~1.

0.

7. The preparation method of a polypropylene cable material with high water tree resistance according to claim 4, characterized in that, In the step of preparing the compatibilized polypropylene, the mass ratio of the polypropylene base material, the polar graft-modified polypropylene and the antioxidant is: 90~110:1~4:0.1~0.

3.

8. The preparation method of a polypropylene cable material with high water tree resistance according to claim 4, characterized in that, In the step of preparing the modified elastomer, the mass ratio of the elastomer base material, the polar graft-modified elastomer, the polar water tree inhibitor and the antioxidant is: 90~110:2~3:5~9:0.1~0.

3.

9. Use of a polypropylene cable material with high water tree resistance according to any one of claims 1-3 in the preparation of power cables.

10. A polypropylene power cable with high water tree resistance performance, characterized in that, The insulating layer is selected from a polypropylene cable material with high water tree resistance according to any one of claims 1-3.

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